1. Field of the Invention
The invention relates generally to drill bits and more particularly to hollow drill bits having openings at the cutting end for supplying a fluid adjacent to the cutting element or for providing a vacuum adjacent to the cutting element and having a bridge supporting the cutting element.
2. Description of the Prior Art
Drill bits having openings at the cutting end to provide a fluid or a vacuum adjacent to the cutting element are known and examples of such drill bits are shown in U.S. Pat. Nos. 2,971,409; 3,010,345; 3,415,332; 3,434,553; 3,434,554; 4,099,585; 4,190,125 and 4,190,128. Additionally, the "DUST HOG" drill bit manufactured by Mining Tools Inc. located in Mentor, Ohio has such openings. In some of the above noted prior art drill bits the openings at the cutting end are located in a quadrant equaling approximately one-half the length of the opposite faces of the cutting element. In other prior art bits noted above the openings at the cutting end extend completely along each face of the cutting element. In all of these prior art drill bits the cutting element is brazed or otherwise fixed in place at the end of the bit in opposed slots cut in the end of the shank of the bit.
In bits having openings which extend only part way along the opposite faces of the cutting element the openings are not large enough to provide a sufficient quantity of fluid or a sufficient vacuum adjacent to the cutting element to achieve the desired drilling speed and efficiency. Drill bits having openings extending completely along the opposite faces of the cutting elements provide larger openings adjacent to the cutting element, but the cutting element is not adequately supported in the bit shank since it is only supported at its ends by the wall of the shank and there is inadequate backup support for the cutting element during drilling.